Zinc (Zn) is an element that can help prevent the oxidation of ferrous materials. Thus, steel may be coated and/or treated with zinc. Some treated materials may produce metal strands known as zinc whiskers. A zinc whisker is a small metal strand that may form on the surface of the treating material. By way of illustration, when ferrous metals like steel are plated with zinc to prevent surface corrosion, molecular level stresses in the plating metal (e.g., zinc) may occur. The crystalline structure within the plating metal may attempt to relieve the internal molecular level stress by enlarging the structure through crystal growth, where the crystals grow out from the plating metal. The crystals that are pushed out of the plating metal can be referred to as zinc whiskers.
Zinc whiskers may grow from the plating metal without external stimuli and have been observed to grow in a vacuum. Zinc whiskers may also be formed in response to the application of an external compressive stress on the plating metal. Similarly, metal “whiskers” can grow from other metals like tin, cadmium, and the like. Zinc whiskers may grow at rates of about 5 microns per year to about 250 microns per year and may be, for example, a few microns in width and several hundred to several thousand microns in length. It is to be appreciated that zinc whiskers and the like may grow at various rates and have various lengths and widths.
Zinc whiskers may originate, for example, from zinc treated (e.g., electroplated) products (e.g., floor tiles) commonly used in computer rooms. For example, a floor tile with a wooden core may have a flat sheet of steel on its bottom that has been treated (e.g., electroplated) with zinc. Over time, zinc whiskers may form on the zinc electroplating on the underside of the floor tile. If the floor tiles are moved during, for example, a computer upgrade, a computer room cleaning, rewiring, and other similar activities, the zinc whiskers may detach from the floor panel and begin circulating in the computer room air supply. The zinc whiskers therefore can become one type of airborne conductive contaminant to which computer circuits, power supplies and the like may be exposed. While floor tiles are described as one source of zinc whiskers, it is to be appreciated that airborne conductive contaminants like zinc whiskers can enter the air supply of a computer room by other manners. Similarly, while a computer room is described, computers, electronics and electrical equipment located in other environments (e.g., office, aircraft, spacecraft, factory) may also be exposed to airborne conductive contaminants like zinc whiskers.
Zinc is an electrically conductive material. Thus, in one example, a zinc whisker may act like a low capacity fuse with a DC resistance of about 10 to 40 ohms depending on the whisker geometry. In another example, a zinc whisker may have a DC fusing current of around 10 to 30 mA. While example zinc whiskers of various sizes, resistances, and fusing currents are described, it is to be appreciated that other airborne conductive contaminants with other sizes, resistances, and fusing currents may be present in the air available to a computer or other electronic component.